1. Field of the Invention
This invention relates to a composition having Vitamin C activity and to a method of making said composition. More particularly, the invention relates to the preparation of crystalline calcium ascorbate. Still more particularly, the invention relates to a method of making a crystalline mixture of calcium ascorbate and calcium ascorbate oxidizate.
2. Description of the Prior Art
Ruskin in U.S. Pat. No. 2,596,103, issued May 13, 1952, and in U.S. Pat. No. 2,631,155, issued Mar. 10, 1953, describes the preparation of crystalline calcium ascorbate dihydrate. (It is pointed that each of Ruskin's examples in each patent contains a common error, namely, 16.3 g of calcium carbonate is stated to equal 1/2 (0.5) mole of calcium carbonate. The molecular weight of calcium carbonate is 100.08. Therefore, Ruskin actually used 16.3 g/100.08 g=0.163 mole (1/6 mole) of calcium carbonate reactant in each of his examples in both patents) Ruskin used in each example in both patents 60 g of ascorbic acid reactant. The molecular weight of ascorbic acid is 176.05. So Ruskin used 60 g/176.05 g=0.342 mole of ascorbic acid. Therefore, Ruskin used a mole ratio of ascorbic acid/calcium carbonate of 0.342/0.163=2.10--the stochiometric amount is 2.0. Thus Ruskin used an excess of ascorbic acid in each of his exemplary procedures.
Ruskin prepares seed crystals of calcium ascorbate dihydrate by reacting, at room temperature, some excess of ascorbic acid in liquid water solution with calcium carbonate; after removing dissolved carbon dioxide gas from the reaction product solution, calcium ascorbate is precipitated from the aqueous solution by a water miscible organic solvent, such as, acetone, methyl alcohol, or ethyl alcohol; the organic solvent is separated to obtain a gummy solid; the gummy solid is dissolved in water; the water is evaporated to recover a crystalline mass of calcium ascorbate dihydrate. (Each of the Ruskin patents at Example 1.)
Ruskin prepares crystalline calcium ascorbate dihydrate in another procedure, as follows: An aqueous solution of calcium ascorbate is prepared by a reaction identical with that used in Example 1; then the aqueous solution is evaporated until a syrup solution is obtained. The syrup is seeded with a few crystals from the batch prepared in Example 1. The seeded syrup solidifies into a solid mass of crystals. The mother liquor is removed by filtering; the crystals are pressed to dryness; and the remaining liquid is removed by washing the crystals with absolute ethyl alcohol. The dry crystals are calcium ascorbate dihydrate. (Each of the Ruskin patents at Example 2.)
In another procedure, Ruskin prepares an aqueous solution of calcium ascorbate by the procedure of Example 1. To this aqueous solution, Ruskin adds a water miscibel organic solvent in an amount controlled to just avoid precipitation of any solid. Then the water-organic solvent solution of calcium ascorbate is seeded with crystals obtained in Example 1. The seeded solution forms prismatic crystals; these crystals were recovered by filtration of the crystal-solution dispersion. The recovered crystals were dried by washing with absolute alcohol; the dry crystals are calcium ascorbate dihydrate. (Each of the Ruskin patents at Example 3.)